The present invention relates to a substrate processing apparatus which provides a plate onto a periphery of a substrate and processes a substrate, and to a method for manufacturing a semiconductor device.
In recent years, in circumstances where a demand for a high-quality semiconductor film has been rising as a semiconductor has been being miniaturized, a film-forming method for forming a deposited film at an atomic layer level by alternately supplying two types of reaction gases has attracted attention. As materials of the reaction gases, gas containing a metal-containing material and gas containing oxygen or nitrogen are used. With regard to the film-forming method, there are two types in terms of a reaction mode. One is atomic layer deposition (ALD), and the other is metal organic chemical vapor deposition (MOCVD) to which a cyclic method is applied. A basic gas supply method is common between these methods, and accordingly, a description will be made of these methods by commonly using FIG. 14. FIG. 14(a) is a flowchart, and FIG. 14(b) is a timing chart of the gas supply. In the illustrated example, the gasified metal-containing material is defined as a material A, and the gas containing the oxygen or the nitrogen is defined as a material B.
The ALD is a method of repeating, plural times, the following four steps as one cycle, which are: a step of supplying the material A to a substrate and allowing the substrate to adsorb the material A (Step 1); a step of, after the adsorption, exhausting the residual material A (Step 2); a step of, after the exhaust, supplying the material B to the substrate and allowing the material B to react with the material A, thereby forming a film (Step 3); and a step of, after the film formation, exhausting the residual material B (Step 4). As shown in FIG. 14(b), gas supply timing is set so that exhaust by purge gas can be sandwiched between the supply of the material A and the supply of the material B, which are alternately performed.
The MOCVD to which the cyclic method is applied is a method of repeating, plural times, the following four steps as one cycle, which are: a step of supplying the material A to a substrate and thermally decomposing the material A, thereby forming a film thereof on the substrate (Step 1); a step of, after the film formation, exhausting the material A (Step 2); a step of, after the exhaustion, supplying the material B to the substrate, thereby performing modification processing for the deposited film (Step 3); and a step of, after the modification, exhausting the residual material B (Step 4). As shown in FIG. 14(b), gas supply timing is set so that exhaust by purge gas can be sandwiched between the supply of the material A and the supply of the material B, which are alternately performed.
In general, it is frequent that reactivity between the material A and the material B is extremely high. When these materials are supplied simultaneously, there occur, owing to a gas phase reaction, generation of a foreign object and deposition of a film inferior in film quality, resulting in reduction of yield. Therefore, in the above-described Steps 2 and 4, evacuation or the purge (exhaust) by inert gas is implemented so that the materials supplied in the previous steps cannot remain. In particular, since the remaining of the materials in an upstream portion of the substrate directly affects film-forming conditions on the substrate, it is required that the purge be performed sufficiently. However, if a time required for the purge is long, then a throughput is reduced.
Meanwhile, in the above-described Steps 1 and 3, in both of the ALD and the MOCVD to which the cyclic method is applied, supplied amounts of the materials A and B onto the substrate are each made uniform, and uniformity in thickness and quality of the film formed on each substrate is enhanced. Here, each supplied amount of the materials is generally conceived to be an arithmetic function of a partial pressure (total pressure×mole fraction of material) of the material. Hence, when each partial pressure of the materials differs between an upstream side and downstream side of a flow of the gas flowing on the substrate, each adsorbed amount thereof does not become uniform, and the uniformity cannot be obtained.
As a semiconductor manufacturing apparatus for implementing the above-described film-forming method, a single wafer apparatus has become a mainstream. In order to control the film thickness highly precisely and form the high-quality film by using the single wafer apparatus, the gas supply and exhaust methods become important from a viewpoint of the above-described uniformity in film thickness and of the throughput. A gas supply/exhaust mode of the single wafer apparatus to the substrate can be broadly divided into the following two modes in terms of a construction.
As shown in FIG. 15(a), one (radial flow type) of the modes is of a method of vertically supplying the gas to a center portion of a substrate surface 43 from a gas supply port 42 on an upper portion of a substrate holding region 41 in a processing chamber 50, the substrate holding region 41 holding the substrate therein, flowing the gas on the substrate surface 43 in a radial direction, and exhausting the gas from an outer circumference of the substrate to an exhaust port 44.
As shown in FIG. 15(b), the other mode (one-side flow type) is of a method of supplying the gas to the substrate surface 43 in parallel thereto from a gas supply port 46 provided on one side of a substrate holding region 45, flowing the gas on the substrate surface 43 in a single direction, and exhausting the gas from an exhaust port 47 provided on the opposite side to the gas supply port 46.
In the case of the radial flow type in FIG. 15(a), an abnormal point in which the film is formed to be abnormally thick occurs on the center portion of the substrate, onto which the gas abuts, and the uniformity in film thickness is deteriorated. In order to avoid such a deterioration, the apparatus of this mode is modified as shown in FIG. 15(c) so that the gas can be flown from the respective holes of a shower plate 48 disposed between the gas supply port 42 and the substrate surface 43. However, a deviation occurs in the gas flow on the wafer owing to a difference in distance from the exhaust port 44 to the respective holes, and accordingly, the supply of the gas onto the substrate surface 43 cannot be made uniform, and it is difficult to ensure the uniformity in film thickness.
In this connection, in the radial flow type, heretofore, a variety thereof aiming to improve the uniformity in film thickness by adjusting conductance of the gas exhaust passage has been thought up. For example, there have been proposed: the one in which cross-sectional areas of flow passages of exhaust conductance adjustment holes on a side of a baffle plate, which is close to an exhaust hole, are made smaller than those on the opposite side in order to make the flow of the reaction gases uniform over the entire surface of the substrate (for example, refer to Japanese Patent Laid-Open Publication No. H08-8239 (published in 1996)); the one including a baffle plate, and changing an interval between baffle holes, a baffle hole diameter, a baffle plate thickness, a slit width, and the like, and so on, thereby being adapted to flow out the exhaust gas in a radius direction at a uniform flow rate free from an uneven distribution over the entire circumferential angle of the wafer (for example, refer to Japanese Patent Laid-Open Publication No. 2001-179078); the one changing an opening distribution of an exhaust passage by moving a baffle plate, thereby changing each exhaust conductance of an exhaust port and an opposite side thereto, thereby adjusting a pressure distribution in a processing space (for example, refer to Japanese Patent Laid-Open Publication No. 2003-68711); and the like.